Magnet mercury switch



Nov. 24, 1959 R. w. HOUSER MAGNET usncuav swncu Filed April 26, 1957 INVENTOR. R01 Wfiovsez:

EH5 ATTORREY United States Patent MAGNET MERCURY SWITCH Roy W. Houser, Anaheim, Calif., assignor to Robertshaw- Fulton Controls Company, Richmond, Va., a corporation of Delaware Application April 26, 1957, Serial No. 655,259

8 Claims. (Cl. 200-112) This invention relates to improvements in electric switches and particularly to a magnet actuated mercury switch.

An object of this invention is to complete an electric circuit by displacement of a body of liquid conductor within a switch housing.

Another object of this invention is to move a liquid conductor between different sized chambers in a switch housing for controlling an electric circuit.

A further object of this invention is to eliminate the necessity of level installation of a mercury switch by displacing the level of a body of mercury from a large chamber to "a relatively small chamber of a switch housing.

It is another object of thisinvention to complete an electric circuit between electrodes with the level of a body of mercury which is displaced from the float chamber to the electrode chamber of a switch housing by the movement of an attractable element under the influence of a magnetic field.

This invention has another object in utilizing an apertured magnetic element to displace a body of mercury therethrough within a switch housing by a cooperating magnetic element exterior of the housing.

This invention has a'further object in that a condition responsive member moves a magnetic element within adjustable limits to vary a magnetic flux encompassing a cooperating magnetic element normally floating on a body of mercury within a sealed housing.

In the construction of this device, a shell of non-ferrous material and a cap of non-ferrous material are hermetically sealed to form a housing having a small upper chamber for a pair of spaced electrodes and a relatively large lower chamber for a body of mercury. Having a relatively low density, an apertured keeper of magnet iron floats on the body of mercury while a corrugated spring washer, immersed in the mercury, aids in the floating support of'the keeper. The movement, within adjustable limits, of a permanent magnet mounted on a condition responsive lever exteriorly of the housing varies'the magnetic flux encompassing the keeper. An increase in flux displaces the keeper into the mercury which is forced through the apertured keeper so that the level of the mercury forms an arcuate bridge in the upper chamber to contact the electrodes; a decrease in flux returns the keeper to a floating position on the relatively higher density mercury while the biasing force exerted by the resilient washer provides a snap action movement to the keeper. Such a construction has unique advantages in the economical manufacture of a precision mercury switch that is relatively small in size, reliable in operation, and capable of functioning in positions other than a vertical position.

Additional features and advantages will become ap- 2,914,633 Patented Nov. 24, 1959 Fig. 1 is a front elevation view of a mercury switch embodying the present invention;

Fig. 2 is a view similar to Fig. 1 with certain parts shown in section illustrating the switch in an open position; and I Fig. 3 is a view similar to Fig. 1 with certain parts shown in section illustrating the switch in a closed positron.

There is shown in the drawing a switch housing, indicated generally at 10, having an upper cover 12 of nonfer-rous material hermetically sealed to a lower cupshaped shell 14 of non-ferrous material. The interior of shell 14 forms a float chamber 16 and the interior of a centrally disposed projection 18, integral with cover 12, is bored to form an electrode chamber 20. As is illustrated in Fig. 2, the volume of float chamber 16 is sub stantially larger than the volume of electrode chamber 20 for a purpose to be described hereinafter. A pair of electric conducting terminals, in the form of electrodes 22, are sealed into cover projection 18 with their inner ends terminating equally and extending in spaced relation into electrode chamber 20 and their outer ends attached to a pair of lead wires 24 by any suitable means such as soldered joints 26.

A predetermined quantity of a liquid conductor in the form ofrnercury 30 is contained in the bottom portion of shell 14 so that the mercury 30 only partially fills float chamber 16. A movable keeper 32 consisting of a magnet-iron ring movably fits within the lateral confines of chamber 16 and is provided with a concentrically disposed aperture 34. The. upper and lower surfaces of keeper ring 32 taper increasingly and radially outwardly from its inner circumference at aperture 34 to its outer circumference. While keeper 32 may be made of any magnetizable material, the selection of such material and the particular dimensions of the ring are designed such that the density of keeper 32 is lower than the density of the body of mercury 30. With keeper 32 positioned on top of mercury 30, the buoyant action of the liquid mercury on keeper 32 provides a floating support therefor. A corrugated resilient spring washer 36 is immersed in the-liquid mercury between the lower surface of keeper 32 and the bottom of float chamber 16. In its free corrugated form, the Washer 36, as shown in Fig. 2, is smaller in diameter than the float chamber 16 to permit a flattening or collapsing action of the washer 36 under certain conditions as will be apparent hereinafter. Normally, the biasing action of spring washer 36 combines with and acts as an aid to the buoyant action of mercury 30 in floatingly supporting keeper 32.

Exterior of the switch housing '10, a switch actuating member 40 has one end fixed to any suitable casing (not shown). While member 40 may be the actuating lever of any condition responsive device, it is disclosed as a flat bimetal strip whose free end moves in response to temperature variations as is well known in the art. A permanent magnet 42 is rigidly secured to bimetal strip 40 adjacent its free end and, as is illustrated in Figs. 2 and 3, magnet 42 is positioned in proximity to and in alignment with housing 10. An adjusting screw 44 threadedly extends through bimetal strip 40 and the center of magnet 42 and has an'abutting end 46 engageable with the exterior bottom of shell 14.

The housing 10 and actuating member 40 are separately fixed within any conventional casing (not shown) in such relative positions that magnet 42 is aligned with housing 10. When the switch is in an open position (Fig. 2) keeper 32 because of its lower density and with the aid of spring washer 36, floats on the body of mercury 30 which has a top level extending approximately half way through aperture 34 of keeper 32. The operation of the switch of the particular embodiment disclosed is responsive to changes in temperature so that as the temperature varies in one direction, the bimetal actuating member 40 causes movement of magnet 42 toward the fixedhousing 10. As a conse quence, the magnetic field of magnet 42 permeates the magnet-iron keeper 32 and the closer that magnet 42 moves toward housing 10, the greater the amount of flux induced in keeper 32. When the magnetic force exceeds the resultant force of the combined biasing ac tion of spring washer 36 and the bouyant action of mercury 30, the keeper 32 is attracted toward magnet 42 thus collapsing the corrugated spring washer 36. It should be noted that even though the temperature variation is a gradual change resulting in a gradual increase in the magnetic force exerted on keeper 32, the final movement of keeper 32 is accomplished with a snap action due to the final collapsing of the corrugated spring washer 36.

As is illustrated in Fig. 3, movement of keeper 32 displaces the liquid mercury through its aperture 34 into the upper portion of float chamber 16 and into the electrode chamber 20 where it forms an arcuate bridge between the spaced electrodes 22 to complete an electric circuit therebetween. Should the switch be mounted in any position within 45 of the vertical, the curved shape of the top level of liquid mercury will not noticeably change because only its radius of curvature will shift to a plane coincident with the force of gravity.

When the temperature varies in the opposite direction, bimetal element causes movement of magnet 42 away from the fixed housing 10. The magnetic force is thus decreased to a point where keeper 32 is released so that corrugated spring washer 36 returns keeper 32 with a snap action to its floating position on mercury 30. Return movement of keeper 32 displaces the mercury 30 to its original position in float chamber 16 thus breaking the electric circuit between the spaced electrodes 22.

Because of the relative small size of this mercury switch it may be incorporated with a straight bimetal type thermostat and still obtain the desired operating characteristics of a small switch angle which controls the thermostat differential of a conventional type mercury switch. The mercury switch of this invention does not have a switch angle inasmuch as the thermostat differential is controlled by the proximity of the magnet. Furthermore, the adjusting screw 44 is adjustable to vary the proximity of magnet 42 to housing 10 as shown in Fig. 3, whereby the switch can be adjusted to a selected switch differential.

Only one embodiment of the invention has been shown and described herein and inasmuch as this invention is subject to many variations, modifications and reversal of parts, it is intended that all matter contained in the above description of the embodiment shown and described shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In an electric switch, the combination comprising a pair of axially disposed chambers, a pair of electric conductors extending into one of said chambers, a liquid conductor contained wholly in the other of said chambers, movable means normally floating on said liquid conductor and having a passage therein disposed coaxially of the one of said chambers to establish communication between said chambers and means exterior of said chambers controlling the movement of said movable means into said liquid conductor to cause a portion thereof to be displaced through said passage into the one of said chambers and form an electric bridge for said conductors therein.

2. The combination as recited in claim 1 wherein the said one of said chambers is relatively smaller than the said other of said chambers so that the level of the liq uid conductor displaced into the smaller chamber forms an arcuate bridge having a radius of curvature in a plane coincident with the force of gravity.

3. In a switch, the combination comprising a housing having axially disposed upper and lower chambers, 21 pair of spaced electric terminals extending into the upper chamber, a body of mercury disposed wholly within the lower chamber remote from said terminals, first magnetic means floatingly supported on said mercury and having an aperture therethrough disposed coaxially of said upper chamber, second -magnetic means mounted exterior of said housing on a condition responsive actuating member and adapted to cooperate with said first magnetic means, said actuating member being movable in response to condition changes to vary the distance between said first and second magnetic means, said first magnetic means being attracted upon a decrease of the distance to displace said body of mercury through its aperture to form an electrical bridge between said pair of terminals and being released upon an increase of the distance to its floating position on said body of mercury to break the electrtical bridge between said pair of terminals.

4. A switch comprising a housing having a pair of coaxially superimposed chambers with a pair of electrodes extending into one of the chambers and a liquid conductor disposed wholly within the other of the chambers, an attractable element normally floating on said liquid conductor, means on said element disposed coaxially of said chambers to establish comunication be tween the pair of chambers, and means exterior of said housing to attract said element into the liquid conductor causing displacement of the same through said first named means into said one of the chambers whereby an electric circuit is completed across said pair of electrodes.

5. A switch comprising a housing having upper and lower cylindrical chambers, a pair of electric terminals extending into the upper chamber, a liquid conductor disposed wholly within the lower chamber, a magnetically attractable element movable in the lower chamber and normally floating on said liquid conductor, said element having an aperture therethrough in axial alignment with the upper of said chambers and defining a passage to establish communication between said upper and lower chambers, and means exterior of said housing to attract said element into said liquid conductor, the movement of said element causing said liquid conductor to be displaced through said aperture into the upper chamber to establish a circuit across said pair of electric terminals.

6. A switch comprising a sealed housing having an electrode chamber and a float chamber, a pair of sealedin electrodes extending into said electrode chamber, a liquid conductor disposed within said float chamber, a magnetically attractable keeper normally floating on said liquid conductor and being movable to displace the same, resilient means in said float chamber aiding in support of said keeper on said liquid conductor, means defining an opening in said keeper permitting flow of said liquid conductor therethrough, and magnetic means exterior of said housing to attract said keeper whereby said liquid conductor is displaced through said opening to contact said pair of electrodes.

7. In a thermostatic switch, the combination comprising a shell of non-ferrous material, a cover of non-ferrous material, said shell and cover being hermetically sealed to form a switch housing, a pair of spaced electrodes extending into said housing, a body of mercury contained within said housing and being displaceable to contact said electrodes, a keeper of magnetizable material havlng a density relatively lower than said mercury whereby said keeper is floatingly supported on said mercury, means defining a centrally disposed aperture in said keeper whereby said mercury is displaceable therethrough, a resilient Wa er immersed in .said mercury and aidmg said mercury to support said keeper, a permanent magnet positioned exterior of and adjacent to said housing, a bimetal element supporting said magnet, said bimetal element being movable in response to variations in temperature to move said permanent magnet toward said housing causing attraction of said keeper into said mercury to displace said mercury into contact with said electrodes and away from said housing causing return of said keeper to its floating position with a snap-action under the bias of said resilient washer, and adjusting means on said permanent magnet to vary the point of actuation of the switch.

8. In a switch, the combination comprising a pair of axially disposed chambers, a pair of electric conductors extending'into one of said chambers, a liquid conductor contained wholly in the other of said chambers, movable means normallyv floating on said liquid conductor and having a passage therein disposed coaxially of the one of said chambers to establish communication between said chambers, resilient means aiding in support of said 20 movable means on said liquid conductor, a condition responsive actuating member mounted exterior of said housing, magnetic means mounted on said condition responsive actuating member and adapted to cooperate with said movable means, said actuating member being mo'v able in response to condition changes to vary the distance between said movable means and said magnetic means, said movable means being attracted upon a decrease of the distance to compress said resilient means and displace a portion of said liquid conductor through said passage to form an electrical bridge between said pair of conductors and being moved to its floating position on said liquid conductor by said resilient means upon an increase of the distance to break the electrical bridge between said pair of terminals.

UNITED STATES PATENTS References Cited in the file of this patent 1,558,277 Phelan et al Oct. 20, 1925 2,658,124 Weimer Nov. 3, 1953 2,709,738 Walker May 31, 1955 

